I'm revisiting the radiance for my current campaign and I thought I'd share my work here. I'm building upon ideas put forward by others both on the MMB and on the MML, most notably Havard, and Rodger Burns, so I'd like to acknowledge them and thank them for sharing their own material. I'm sure there are others who have influenced me on this topic as well, but those two have recently rekindled my interest in this topic.

The Radiance Revisited

Dealing with the radiance can be hazardous to one's health. There are several circumstances where a character can become afflicted by radiance poisoning. A character must make a fortitude save or become poisoned. The effects of radiance poisoning are not always predictable, and are detailed below. Roll 1d4 to determine the specific effect that radiance poisoning has on the character.

It is possible for radiance poisoning to have both a primary and a secondary effect (dependant upon the severity of the poisoning. In cases where a secondary effect is warranted, simply roll a second time on the table below to determine the type. The primary and secondary poisoning effects need not be identical.

Damage caused by radiance poisoning heals at the normal rate. If any ability score is dropped to zero due to radiance poisoning, the character must immediately make an additional fortitude save at DC 20 or suffer the effects of radiance corruption.

Table: Radiance Poisoning

1d4

Effect

1

Loose 1d2 Str

2

Loose 1d2 Dex

3

Loose 1d2 Con

4

Loose 1d2 Cha

RADIANCE CORRUPTION

Wielding the most powerful and potent forms of the radiance can sometimes be more dangerous than mere exposure to it. In these circumstances the radiance can permanently corrupt a portion of a character's body. This corruption can not be healed by any mortal means (not even through the use of a wish spell).

Re-roll duplicate results. Once all of a characters body has been corrupted they become a Radiance Lich.

Table: Radiance Corruption

1d20

Body part

1-2

Left hand

3-4

Right Hand

5-6

Right arm

7-8

Left arm

9-10

Left leg

11-12

Right leg

13-14

Right foot

15-16

Left foot

17-18

Torso

19-20

Face/Head

STORING RADIANCE

The radiance can be stored in certain magical items, as well as within the bodies of characters who know how. For each day that a character stores Rads within his own body, or is exposed to raw radiance (or that stored in Radiance Rods) he must make a fortitude save (DC of 10 + stored Rads) or suffer from radiance poisoning.

RADIANCE CLASSES

BROTHER OF RAD [Adapted from the Radiance Mage by Havard.]
Hit Die: d4.

Requirements
To qualify to become a Brother of Rad, a character must fulfil all the following criteria.
Skills: Knowledge (arcana) 9 ranks, Spellcraft 9 ranks.
Special: A character must have built a radiance receptacle and have been contacted and sponsored by a member of the Brotherhood of Rad.

All of the following are class features of the Brother of Rad prestige class.

Weapon and Armour Proficiency: Brothers of Rad gain no proficiency with any weapon or armour.

Spells per Day/Spells Known: When a new Brother of Rad level is gained, the character gains new spells per day (and spells known, if applicable) as if she had also gained a level in a spellcasting class she belonged to before she added the prestige class. She does not, however, gain any other benefit a character of that class would have gained. This essentially means that she adds the level of Brother of Rad to the level of some other Brother of Rad class the character has, then determines spells per day, spells known, and caster level accordingly.

Brotherhood Contacts: Once the Brother of Rad has created a Radiance Receptacle, he is contacted by the Brotherhood of the Radiance through the receptacle. At 1st level he is able to contact other members of the Brotherhood and may ask them for advice or help. The members are extremely secretive about their identities and will not do anything that will make them reveal this, even to other Radiance Members. Furthermore, members will want something in return for favours done.

Transcendence: Once the Brother of Rad reaches 5th level the secrets of the radiance spell Transcendence are revealed to him. The Brother of Rad must still spend the required amount of time and gold in order to research the specifics of the spell, and they must gather all of the material components required to cast it. Once the spell has been researched and the material components gathered, the Brother of Rad may attempt to cast the spell. The Brother of Rad may attempt any number of castings, but each one consumes all of the material components, whether the spell is successful or not.

RADIANT SHAMAN
Hit Die: d6

Requirements
To qualify to become a Radiant Shaman, a character must fulfil all the following criteria.
Skills: Knowledge (religion - Rafiel) 8 ranks.
Special: A character must be inducted into the Order of Shamans and receive the blessings of Rafiel. Induction usually requires that the character receive and pass some type of quest or test.

All of the following are class features of the Radiant Shaman prestige class.

Eschew Ingestion: Unlike others who use the power of the radiance, a Radiant Shaman with a soul crystal does not need to ingest the radiance before using it. Whenever casting a spell with a number of Rads as a material component, the Radiant Shaman may draw those Rads directly from a soul crystal. A Radiant Shaman not in possession of a soul crystal would still need to ingest radiance to cast radiance spells normally (and in that case would need to possess something like the Ingest Radiance feat).

Soul Link: Once the Radiant Shaman reaches 2nd level she is able to establish a closer bond to the souls that inhabit soul crystals. The Radiant Shaman is able to call upon one and a half times the normal number of Rads stored in a given soul crystal. Doing so causes the soul crystal to lay dormant for a period of one day so that the souls within can recover.

Soul Consumption: Once the Radiant Shaman reaches 4th level she begins to understand the true nature of soul crystals as receptacles of the Radiance, and not receptacles of souls. The Radiant Shaman is able to call out double the number of Rads that a given soul crystal stores. Doing so damages the crystal causing its total Rad storage capacity to diminish by 1. Once a soul crystal has been depleted of all of its Rad storage capacity, it crumbles to dust.

Transcendence: Once the Radiant Shaman reaches 5th level the secrets of the radiance spell Transcendence are revealed to him. The Radiant Shaman must still spend the required amount of time and gold in order to research the specifics of the spell, and they must gather all of the material components required to cast it. Once the spell has been researched and the material components gathered, the Radiant Shaman may attempt to cast the spell. The Radiant Shaman may attempt any number of castings, but each one consumes all of the material components, whether the spell is successful or not.

RADIANCE FEATS

TOUCHED BY RAD/RAFIEL [GENERAL]
Prerequisite: Int 13, Exposure to the radiance (determined by DM).
Benefit: You gain the Radiance subtype and the ability to take Radiance feats, as well as cast radiance spells (if you are a spellcaster).

INGEST RADIANCE [RADIANCE]
Prerequisite: Must have acquired the Radiance subtype.
Benefit: You are able to ingest 1d6 radiance points directly from a radiance power source (The Nucleus of the Spheres, a radiance receptacle, a soul crystal, a radiance rod, etc.). There is no limit on the number of times that you can ingest the radiance, however each time the radiance is ingested you must make a fortitude save (DC 10 + the number of Rads ingested) or suffer the effects of radiance poisoning. The total number of Rads stored at one time can never exceed your character level.
Rads may be used as material components to power radiance spells (see individual spell descriptions for requirements).
Normal: You are not able to ingest any radiance points. The total number of Rads that you are able to retain in your own body (should you find some means of doing so) is equal to your character level.

IMPROVED INGEST RADIANCE [RADIANCE]
Prerequisite: Must have acquired the Radiance subtype, Ingest Radiance.
Benefit: You are able to ingest 1d8 radiance points directly from a radiance power source (The Nucleus of the Spheres, a radiance receptacle, a soul crystal, a radiance rod, etc.). There is no limit on the number of times that you can ingest the radiance, however each time the radiance is ingested you must make a fortitude save (DC 10 + the number of Rads ingested) or suffer the effects of radiance poisoning. The total number of Rads stored at one time can never exceed your character level times 2.

RADIANCE FORTITUDE [RADIANCE]
Prerequisite: Must have acquired the Radiance subtype.
Benefit: Add +4 to any Fortitude save when trying to resist radiance poisoning or corruption.
Normal: A fortitude save against radiance corruption receives no bonus.

INFUSE RADIANCE [METAMAGIC]
Prerequisite: Must have acquired the Radiance subtype.
Benefit: Reduces a spell's spell slot by one for every 5 Rads spent. This metamagic feat can only be used in conjunction with other metamagic feats, and its use never reduces a spell slot below what the spell would normally be cast at.
Spells are prepared in advance as normal, but Rads are spent only at the time of casting. If insufficient Rads exist to power this metamagic feat, then the spell can not be cast. Using Radiance in this way may cause radiance corruption (determined by the level of the spell before this feat is applied to it).

IMBUE RADIANCE [METAMAGIC]
Prerequisite: Must have acquired the Radiance subtype.
Benefit: Imbues the spell with the power of the radiance. Anyone effected by the spell must make an additional fortitude save or suffer radiance poisoning. An imbued spell uses up a spell slot one level higher than the spell's normal level.
Spells are prepared in advance as normal, but Rads are spent only at the time of casting. If insufficient Rads exist to power this metamagic feat, then the spell can not be cast. Using Radiance in this way may cause radiance corruption (determined by the level of the spell after this feat is applied to it).

RADIANCE SPELLS

Eschew Materials
Radiance
Level: Sor/Wiz 3, Clr 3
Components: M
Casting Time: 1 free action
Range: Personal
Target: You
Duration: 1 min./level
Saving Throw: Will negates (harmless)
Spell Resistance: Yes
You can cast any spell that has a material component costing 1 gp or less without needing that component. (The casting of the spell still provokes attacks of opportunity as normal.) If the spell requires a material component that costs more than 1 gp, you must have the material component at hand to cast the spell, just as normal.
Material Component: 1 Rad

Call Upon Radiance [modified from Rodger Burns]
Radiance
Level: Sor/Wiz 5, Clr 5
Components: V, M
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: Instantaneous
The caster calls upon the radiance to enhance the next spell that he casts by applying a metamagic feat to it. You do not have to choose metamagic feats known to you for this. Casting a spell in this way does not extend its casting time (as it would normally when using a metamagic feat), but it does incur a fortitude save to avoid radiance poisoning. The save is made at the DC of the spell level + the number of Rads spent.
Empower - 2 Rads.
Enlarge - 1 Rad.
Extend - 1 Rad.
Heighten - (Effective level - real level) Rads.
Maximise - 3 Rads.
Quicken - 4 Rads.
Silent - 1 Rad.
Widen - 3 Rads.
Material Component: Rad points (variable).

Control Destiny [Rodger Burns]
Radiance
Level: Sor/Wiz 7, Clr 7
Components: V, S
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 1 round/level
Saving Throw: Will negates (harmless)
Spell Resistance: Yes
This spell allows you to use raw Radiance energy to shape the balance of time and space around you. While this spell is in effect, you may take a free action (concentrating on the spell) and expend Rads to apply an unnamed bonus or penalty to any action being taken that you're aware of - your own, an ally's, or an enemy's. For each Rad expended, you can provide a +1 bonus or a -1 penalty. A maximum of 10 Rads can be spent to affect any action.
[Roger Burns: Design Notes: The raw, unnamed bonus/penalty is cleaner than trying to change die rolls or force rerolls, especially given the possibility of changing an attack die roll into a 20 and insuring a critical. The 10 Rads limit just makes sense, given the balance limitations on other 3E material.]
Material Component: Rad points (variable).

Retain Power
Radiance
Level: Sor/Wiz 3, Clr 3
Components: V, S, F
Casting Time: 10 minutes
Range: Personal
Target: You
Duration: Instantaneous
Saving Throw: Will negates (harmless)
Spell Resistance: Yes
The Radiance infuses the target of the spell and fills them with 1d6 Rad points. A character can normally retain a number of Rads within their own body equal to their character level.
Focus: A radiance receptacle or other point of radiance power.

Summon Radiance
Conjuration
Level: Sor/Wiz 6, Clr 6
Components: V, S
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 1 round./level
Saving Throw: Will negates (harmless)
Spell Resistance: Yes
The caster of this spell can call upon the radiance from a great distance to an actual radiance power source. While this spell is in effect the caster may act as if he is in direct contact with a radiance power source. Spells requiring a radiance power source as a Focus may be cast normally.

Transcendence [modified from Rodger Burns]
Radiance
Level: Sor/Wiz 9, Clr 9
Components: V, S, M, F
Casting Time: 1 day
Range: Personal
Target: You
Duration: Instantaneous
The caster has a chance to become an Immortal. Once the spell is cast, the caster must make a DC 50 Will save. Success means that you attain immortality. Failure utterly destroys your soul.
Material Component: Lots of crazy impossible stuff.
Focus: A radiance receptacle or other point of radiance power.

MAGIC ITEMS (RADIANCE ITEMS)

Radiance Receptacle: A radiance receptacle can take nearly any shape or form, but they all share some things in common. The focal point of a radiance receptacle is a large spherical crystal that is usually set upon a pedestal of some type. The radiance receptacle is usually so large that it can not easily be moved.
Any radiance spells cast within the vicinity (100 ft.) of a radiance receptacle may forgo the need for Rad expenditure. This means that a radiance mage does not need to ingest or otherwise store radiance points before casting a radiance spell as long as they are near to a receptacle.
Strong radiance; CL ?th; Craft Wondrous Item?, others?; Price xx,xxx gp; Weight 750 lb.

Radiance Rod: These small rods are not magical in and of themselves, however they can carry great power. A radiance rod is 1 foot long and 1 inch in diameter, and usually comes sealed in a lead lined scroll casing. Radiance rods can store 5, 10, 15, or 20 Rad points. Anyone with the ability (see the Ingest Radiance feat) can use the rod as if it were a radiance power point. Radiance points that are taken from the rod do not replenish automatically, though those that know how can replenish them.
Being exposed to an unprotected radiance rod (one that is not kept in a lead container) for more than one hours worth of time can cause Radiance Poisoning. Each hour of unprotected exposure will force anyone within 30 feet of the rod to make a fortitude save at DC 10 + the number of Rads currently stored in the rod or become poisoned. Exposure to multiple rods raises the save DC to 10 + the sum of Rads currently stored in each of the rods.
Moderate radiance; CL ?th; Craft Wondrous Item?, others?; Price x,xxx gp; Weight 7 lb.

Soul Crystal: Soul crystals are naturally occurring radiance receptacles, and can be used as such with the following exceptions. Soul crystals are capable of holding from 1 to 10 Rads at any given time (depending upon the quality of the crystal. Rads replenish in the crystal automatically each round, but a character can never make use of more than the maximum number of Rads storable in a single round. For example a Radiance Shaman could use a 3 Rad crystal to supply the material component of any Radiance spell that uses 3 Rads or less, but could never pay more than 3 Rads per round. The Shaman could also ingest 3 Rads per round from the same crystal, thus building up a larger Rad reserve, but would suffer all of the ill effects associated with doing so.
In addition to being rare, soul crystals are extremely fragile and cannot withstand exposure to the sun in any way. As soon as they are brought forth from the reaches of the dark earth caverns where they are found, a soul crystal will crumble to dust.
Moderate radiance; Weight 1-5 lb.

Bracers of Radiance Resistance: When worn, these bracers provide the wearer with a +2, +4, or +6 bonus to all fortitude saves made against radiance effects (either poisoning, or corruption). Both bracers must be worn to be effective.
Moderate radiance; CL ?th; Craft Wondrous Item?, Craft Magic Arms and Armour; Price x,xxx gp; Weight 1 lb.

Benekander's Bracers: This artifact was crafted by the immortal Benekander. They provide a +6 bonus to all fortitude saves made against radiance effects (just as Bracers of Radiance Resistance). Three times per day, for one hour each use, they may also be used to completely negate the effects of radiance poisoning (but not radiance corruption).
Very strong radiance; CL ?th; Craft Wondrous Item?, Craft Magic Arms and Armour; Price x,xxx gp; Weight 1 lb.